Lily's Ghosts book by Laura Ruby

Lily is Furious.
She can't believe she has to move again after her mom's break-up with the latest boyfriend. Now they're broke and they'll have to spend the winter in Uncle Wes's creepy summerhouse in Cape May, New Jersey.

And the place is crawling with ghosts.

From the spiteful teenager who mistakes Lily for her high school nemesis to the restless spirit of her eccentric Uncle Max, Lily is haunted by a host of unhappy phantoms. But why are they here? And what do they want?

With the help of some mysterious clues, Lily and her new friend, local boy Vaz, uncover a sinister plot. If they don't foil the villainous plan in time, they may end up doing some eternal haunting of their own.